The oxidation of free coelenterazine by superoxide anion was analyzed and compared to the oxidation by the semisynthetic photoprotein obelin, prepared by incorporation of synthetic coelenterazine into apoobelin. The oxidation of bound coelenterazine was triggered upon binding of calcium to the reconstituted photoprotein. The oxidation of free synthetic coelenterazine, in the absence of the apoprotein, was triggered by superoxide anion. The production of reactive oxygen metabolites by fMet-Leu… CONTINUE READING